This application is generally directed to a stored energy system and method and, in one or more embodiments, is particularly directed to a backup power system, a controller useful therein, and a method for providing backup power having application, for example, in support of a computer system or other devices that require a stable source of electrical power for continuous, uninterrupted operation and protection of sensitive electronic components.
Conventional emergency and redundant power systems supporting offline or near-line cogeneration or emergency standby generation are generally limited in their ability to meet end-users' goal of continuous, interruptible power. Such conventional systems typically employ a primary utility feed, a transfer switch and, on the other switched side of the transfer switch, a generator powered by a prime mover, e.g., a diesel engine.
The output of the transfer switch typically feeds an uninterruptible power supply (UPS) or other stored energy system (e.g., a mechanical flywheel). Transfer switch logic may be designed to power up and switch to the generator when the utility mains fail for longer than a specified amount of time. After utility power has been restored for a sufficient period of time, the transfer switch is designed to switch back to the utility mains or primary source of power. The stored energy system may provide power and energy shaping in the time gaps or interruptions between generator fire-up, as well as during the transfer switch switching delay.
As the electrical supply grid becomes more complex with multiple energy providers, multiple grids, and increased loading, a number of failures less than a total outage during a single fault event often occur. For example, during failure of a transformer or during a series of lightning strikes in the power grid, power may intermittently disappear and reappear on the utility feed several times within a short period of time. Such intermittent power outages may be a precursor to a total power failure, or may damage electronic equipment fed by the grid.
This kind of cycling effect can not only result in power spikes that can damage sensitive electronic equipment, it can drain a stored energy system without allowing sufficient time to recharge between hits. If this sort of event occurs and the stored energy system does not have enough energy to handle the delay for the generator to achieve full power, the end-user's power source will see an interruption and potential damage to components or interruption of service often results.